/* libFLAC - Free Lossless Audio Codec library
 * Copyright (C) 2001,2002,2003,2004,2005,2006,2007  Josh Coalson
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the Xiph.org Foundation nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#if HAVE_CONFIG_H
    #include <config.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__
    #if defined __BORLANDC__
        #include <utime.h> /* for utime() */
    #else
        #include <sys/utime.h> /* for utime() */
    #endif
    #include <io.h> /* for chmod() */
    #include <sys/types.h> /* for off_t */
    #if _MSC_VER <= 1600 || defined __BORLANDC__ /* @@@ [2G limit] */
        #define fseeko fseek
        #define ftello ftell
    #endif
#else
    #include <sys/types.h> /* some flavors of BSD (like OS X) require this to get time_t */
    #include <utime.h> /* for utime() */
    #include <unistd.h> /* for chown(), unlink() */
#endif
#include <sys/stat.h> /* for stat(), maybe chmod() */

#include "private/metadata.h"

#include "public/assert_flac.h"
#include "public/stream_decoder.h"
#include "share/alloc.h"

#ifdef max
    #undef max
#endif
#define max(a, b) ((a) > (b) ? (a) : (b))
#ifdef min
    #undef min
#endif
#define min(a, b) ((a) < (b) ? (a) : (b))


/****************************************************************************
 *
 * Local function declarations
 *
 ***************************************************************************/

static void pack_uint32_(FLAC__uint32 val, FLAC__byte* b, unsigned bytes);
static void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte* b, unsigned bytes);
static void pack_uint64_(FLAC__uint64 val, FLAC__byte* b, unsigned bytes);
static FLAC__uint32 unpack_uint32_(FLAC__byte* b, unsigned bytes);
static FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte* b, unsigned bytes);
static FLAC__uint64 unpack_uint64_(FLAC__byte* b, unsigned bytes);

static FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator* iterator);
static FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block);
static FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool* is_last, FLAC__MetadataType* type, unsigned* length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata* block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo* block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding* block, unsigned block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application* block, unsigned block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable* block, unsigned block_length);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry* entry);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment* block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track* track);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet* block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture* block);
static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown* block, unsigned block_length);

static FLAC__bool write_metadata_block_header_(FILE* file, FLAC__Metadata_SimpleIteratorStatus* status, const FLAC__StreamMetadata* block);
static FLAC__bool write_metadata_block_data_(FILE* file, FLAC__Metadata_SimpleIteratorStatus* status, const FLAC__StreamMetadata* block);
static FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata* block);
static FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata* block);
static FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo* block);
static FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding* block, unsigned block_length);
static FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application* block, unsigned block_length);
static FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable* block);
static FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment* block);
static FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet* block);
static FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture* block);
static FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown* block, unsigned block_length);

static FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator* iterator, const FLAC__StreamMetadata* block);
static FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, unsigned padding_length, FLAC__bool padding_is_last);
static FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, FLAC__bool append);

static void simple_iterator_push_(FLAC__Metadata_SimpleIterator* iterator);
static FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator* iterator);

static unsigned seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb);
static unsigned seek_to_first_metadata_block_(FILE* f);

static FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator* iterator, FILE** tempfile, char** tempfilename, FLAC__bool append);
static FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator* iterator, FILE** tempfile, char** tempfilename, int fixup_is_last_code, off_t fixup_is_last_flag_offset, FLAC__bool backup);

static FLAC__bool copy_n_bytes_from_file_(FILE* file, FILE* tempfile, off_t bytes, FLAC__Metadata_SimpleIteratorStatus* status);
static FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, off_t bytes, FLAC__Metadata_SimpleIteratorStatus* status);
static FLAC__bool copy_remaining_bytes_from_file_(FILE* file, FILE* tempfile, FLAC__Metadata_SimpleIteratorStatus* status);
static FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus* status);

static FLAC__bool open_tempfile_(const char* filename, const char* tempfile_path_prefix, FILE** tempfile, char** tempfilename, FLAC__Metadata_SimpleIteratorStatus* status);
static FLAC__bool transport_tempfile_(const char* filename, FILE** tempfile, char** tempfilename, FLAC__Metadata_SimpleIteratorStatus* status);
static void cleanup_tempfile_(FILE** tempfile, char** tempfilename);

static FLAC__bool get_file_stats_(const char* filename, struct stat* stats);
static void set_file_stats_(const char* filename, struct stat* stats);

static int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence);
static FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle);

static FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status);


#ifdef FLAC__VALGRIND_TESTING
static size_t local__fwrite(const void* ptr, size_t size, size_t nmemb, FILE* stream)
{
    size_t ret = fwrite(ptr, size, nmemb, stream);
    if (!ferror(stream))
        fflush(stream);
    return ret;
}
#else
    #define local__fwrite fwrite
#endif

/****************************************************************************
 *
 * Level 0 implementation
 *
 ***************************************************************************/

static FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder* decoder, const FLAC__Frame* frame, const FLAC__int32* const buffer[], void* client_data);
static void metadata_callback_(const FLAC__StreamDecoder* decoder, const FLAC__StreamMetadata* metadata, void* client_data);
static void error_callback_(const FLAC__StreamDecoder* decoder, FLAC__StreamDecoderErrorStatus status, void* client_data);

typedef struct
{
    FLAC__bool got_error;
    FLAC__StreamMetadata* object;
} level0_client_data;

static FLAC__StreamMetadata * get_one_metadata_block_(const char* filename, FLAC__MetadataType type)
{
    level0_client_data cd;
    FLAC__StreamDecoder* decoder;

    FLAC__ASSERT(0 != filename);

    cd.got_error = false;
    cd.object = 0;

    decoder = FLAC__stream_decoder_new();

    if (0 == decoder)
        return 0;

    FLAC__stream_decoder_set_md5_checking(decoder, false);
    FLAC__stream_decoder_set_metadata_ignore_all(decoder);
    FLAC__stream_decoder_set_metadata_respond(decoder, type);

    if (FLAC__stream_decoder_init_file(decoder, filename, write_callback_, metadata_callback_, error_callback_, &cd) != FLAC__STREAM_DECODER_INIT_STATUS_OK || cd.got_error)
    {
        FLAC__stream_decoder_finish(decoder);
        FLAC__stream_decoder_delete(decoder);
        return 0;
    }

    if (!FLAC__stream_decoder_process_until_end_of_metadata(decoder) || cd.got_error)
    {
        FLAC__stream_decoder_finish(decoder);
        FLAC__stream_decoder_delete(decoder);
        if (0 != cd.object)
            FLAC__metadata_object_delete(cd.object);
        return 0;
    }

    FLAC__stream_decoder_finish(decoder);
    FLAC__stream_decoder_delete(decoder);

    return cd.object;
}

FLAC_API FLAC__bool FLAC__metadata_get_streaminfo(const char* filename, FLAC__StreamMetadata* streaminfo)
{
    FLAC__StreamMetadata* object;

    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != streaminfo);

    object = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_STREAMINFO);

    if (object)
    {
        /* can just copy the contents since STREAMINFO has no internal structure */
        *streaminfo = *object;
        FLAC__metadata_object_delete(object);
        return true;
    }
    else
    {
        return false;
    }
}

FLAC_API FLAC__bool FLAC__metadata_get_tags(const char* filename, FLAC__StreamMetadata** tags)
{
    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != tags);

    *tags = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_VORBIS_COMMENT);

    return 0 != *tags;
}

FLAC_API FLAC__bool FLAC__metadata_get_cuesheet(const char* filename, FLAC__StreamMetadata** cuesheet)
{
    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != cuesheet);

    *cuesheet = get_one_metadata_block_(filename, FLAC__METADATA_TYPE_CUESHEET);

    return 0 != *cuesheet;
}

FLAC__StreamDecoderWriteStatus write_callback_(const FLAC__StreamDecoder* decoder, const FLAC__Frame* frame, const FLAC__int32* const buffer[], void* client_data)
{
    decoder, frame, buffer, client_data;

    return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
}

void metadata_callback_(const FLAC__StreamDecoder* decoder, const FLAC__StreamMetadata* metadata, void* client_data)
{
    level0_client_data* cd = (level0_client_data*)client_data;
    decoder;

    /*
     * we assume we only get here when the one metadata block we were
     * looking for was passed to us
     */
    if (!cd->got_error && 0 == cd->object)
    {
        if (0 == (cd->object = FLAC__metadata_object_clone(metadata)))
            cd->got_error = true;
    }
}

void error_callback_(const FLAC__StreamDecoder* decoder, FLAC__StreamDecoderErrorStatus status, void* client_data)
{
    level0_client_data* cd = (level0_client_data*)client_data;
    decoder;

    if (status != FLAC__STREAM_DECODER_ERROR_STATUS_LOST_SYNC)
        cd->got_error = true;
}

FLAC_API FLAC__bool FLAC__metadata_get_picture(const char* filename, FLAC__StreamMetadata** picture, FLAC__StreamMetadata_Picture_Type type, const char* mime_type, const FLAC__byte* description, unsigned max_width, unsigned max_height, unsigned max_depth, unsigned max_colors)
{
    FLAC__Metadata_SimpleIterator* it;
    FLAC__uint64 max_area_seen = 0;
    FLAC__uint64 max_depth_seen = 0;

    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != picture);

    *picture = 0;

    it = FLAC__metadata_simple_iterator_new();
    if (0 == it)
        return false;
    if (!FLAC__metadata_simple_iterator_init(it, filename, /*read_only=*/ true, /*preserve_file_stats=*/ true))
    {
        FLAC__metadata_simple_iterator_delete(it);
        return false;
    }
    do
    {
        if (FLAC__metadata_simple_iterator_get_block_type(it) == FLAC__METADATA_TYPE_PICTURE)
        {
            FLAC__StreamMetadata* obj = FLAC__metadata_simple_iterator_get_block(it);
            FLAC__uint64 area = (FLAC__uint64)obj->data.picture.width * (FLAC__uint64)obj->data.picture.height;
            /* check constraints */
            if (
                (type == (FLAC__StreamMetadata_Picture_Type)(-1) || type == obj->data.picture.type) &&
                (mime_type == 0 || !strcmp(mime_type, obj->data.picture.mime_type)) &&
                (description == 0 || !strcmp((const char*)description, (const char*)obj->data.picture.description)) &&
                obj->data.picture.width <= max_width &&
                obj->data.picture.height <= max_height &&
                obj->data.picture.depth <= max_depth &&
                obj->data.picture.colors <= max_colors &&
                (area > max_area_seen || (area == max_area_seen && obj->data.picture.depth > max_depth_seen))
                )
            {
                if (*picture)
                    FLAC__metadata_object_delete(*picture);
                *picture = obj;
                max_area_seen = area;
                max_depth_seen = obj->data.picture.depth;
            }
            else
            {
                FLAC__metadata_object_delete(obj);
            }
        }
    }
    while (FLAC__metadata_simple_iterator_next(it));

    FLAC__metadata_simple_iterator_delete(it);

    return (0 != *picture);
}


/****************************************************************************
 *
 * Level 1 implementation
 *
 ***************************************************************************/

#define SIMPLE_ITERATOR_MAX_PUSH_DEPTH (1 + 4)
/* 1 for initial offset, +4 for our own personal use */

struct FLAC__Metadata_SimpleIterator
{
    FILE* file;
    char* filename, * tempfile_path_prefix;
    struct stat stats;
    FLAC__bool has_stats;
    FLAC__bool is_writable;
    FLAC__Metadata_SimpleIteratorStatus status;
    off_t offset[SIMPLE_ITERATOR_MAX_PUSH_DEPTH];
    off_t first_offset; /* this is the offset to the STREAMINFO block */
    unsigned depth;
    /* this is the metadata block header of the current block we are pointing to: */
    FLAC__bool is_last;
    FLAC__MetadataType type;
    unsigned length;
};

FLAC_API const char* const FLAC__Metadata_SimpleIteratorStatusString[] = {
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR",
    "FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR"
};


FLAC_API FLAC__Metadata_SimpleIterator * FLAC__metadata_simple_iterator_new()
{
    FLAC__Metadata_SimpleIterator* iterator = (FLAC__Metadata_SimpleIterator*)calloc(1, sizeof(FLAC__Metadata_SimpleIterator));

    if (0 != iterator)
    {
        iterator->file = 0;
        iterator->filename = 0;
        iterator->tempfile_path_prefix = 0;
        iterator->has_stats = false;
        iterator->is_writable = false;
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
        iterator->first_offset = iterator->offset[0] = -1;
        iterator->depth = 0;
    }

    return iterator;
}

static void simple_iterator_free_guts_(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);

    if (0 != iterator->file)
    {
        fclose(iterator->file);
        iterator->file = 0;
        if (iterator->has_stats)
            set_file_stats_(iterator->filename, &iterator->stats);
    }
    if (0 != iterator->filename)
    {
        free(iterator->filename);
        iterator->filename = 0;
    }
    if (0 != iterator->tempfile_path_prefix)
    {
        free(iterator->tempfile_path_prefix);
        iterator->tempfile_path_prefix = 0;
    }
}

FLAC_API void FLAC__metadata_simple_iterator_delete(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);

    simple_iterator_free_guts_(iterator);
    free(iterator);
}

FLAC_API FLAC__Metadata_SimpleIteratorStatus FLAC__metadata_simple_iterator_status(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__Metadata_SimpleIteratorStatus status;

    FLAC__ASSERT(0 != iterator);

    status = iterator->status;
    iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
    return status;
}

static FLAC__bool simple_iterator_prime_input_(FLAC__Metadata_SimpleIterator* iterator, FLAC__bool read_only)
{
    unsigned ret;

    FLAC__ASSERT(0 != iterator);

    if (read_only || 0 == (iterator->file = fopen(iterator->filename, "r+b")))
    {
        iterator->is_writable = false;
        if (read_only || errno == EACCES)
        {
            if (0 == (iterator->file = fopen(iterator->filename, "rb")))
            {
                iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
                return false;
            }
        }
        else
        {
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
            return false;
        }
    }
    else
    {
        iterator->is_writable = true;
    }

    ret = seek_to_first_metadata_block_(iterator->file);
    switch (ret)
    {
        case 0:
            iterator->depth = 0;
            iterator->first_offset = iterator->offset[iterator->depth] = ftello(iterator->file);
            return read_metadata_block_header_(iterator);
        case 1:
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        case 2:
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
            return false;
        case 3:
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE;
            return false;
        default:
            FLAC__ASSERT(0);
            return false;
    }
}

#if 0
@@@ If we decide to finish implementing this, put this comment back in metadata.h
/*
 * The 'tempfile_path_prefix' allows you to specify a directory where
 * tempfiles should go.  Remember that if your metadata edits cause the
 * FLAC file to grow, the entire file will have to be rewritten.  If
 * 'tempfile_path_prefix' is nullptr, the temp file will be written in the
 * same directory as the original FLAC file.  This makes replacing the
 * original with the tempfile fast but requires extra space in the same
 * partition for the tempfile.  If space is a problem, you can pass a
 * directory name belonging to a different partition in
 * 'tempfile_path_prefix'.  Note that you should use the forward slash
 * '/' as the directory separator.  A trailing slash is not needed; it
 * will be added automatically.
 */
FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator* iterator, const char* filename, FLAC__bool preserve_file_stats, const char* tempfile_path_prefix);
#endif

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_init(FLAC__Metadata_SimpleIterator* iterator, const char* filename, FLAC__bool read_only, FLAC__bool preserve_file_stats)
{
    const char* tempfile_path_prefix = 0; /*@@@ search for comments near 'rename(...)' for what it will take to finish implementing this */

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != filename);

    simple_iterator_free_guts_(iterator);

    if (!read_only && preserve_file_stats)
        iterator->has_stats = get_file_stats_(filename, &iterator->stats);

    if (0 == (iterator->filename = _strdup(filename)))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
    }
    if (0 != tempfile_path_prefix && 0 == (iterator->tempfile_path_prefix = _strdup(tempfile_path_prefix)))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
    }

    return simple_iterator_prime_input_(iterator, read_only);
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_writable(const FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    return iterator->is_writable;
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_next(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    if (iterator->is_last)
        return false;

    if (0 != fseeko(iterator->file, iterator->length, SEEK_CUR))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    iterator->offset[iterator->depth] = ftello(iterator->file);

    return read_metadata_block_header_(iterator);
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_prev(FLAC__Metadata_SimpleIterator* iterator)
{
    off_t this_offset;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    if (iterator->offset[iterator->depth] == iterator->first_offset)
        return false;

    if (0 != fseeko(iterator->file, iterator->first_offset, SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }
    this_offset = iterator->first_offset;
    if (!read_metadata_block_header_(iterator))
        return false;

    /* we ignore any error from ftello() and catch it in fseeko() */
    while (ftello(iterator->file) + (off_t)iterator->length < iterator->offset[iterator->depth])
    {
        if (0 != fseeko(iterator->file, iterator->length, SEEK_CUR))
        {
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
            return false;
        }
        this_offset = ftello(iterator->file);
        if (!read_metadata_block_header_(iterator))
            return false;
    }

    iterator->offset[iterator->depth] = this_offset;

    return true;
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_is_last(const FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    return iterator->is_last;
}

/*@@@@add to tests*/
FLAC_API off_t FLAC__metadata_simple_iterator_get_block_offset(const FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    return iterator->offset[iterator->depth];
}

FLAC_API FLAC__MetadataType FLAC__metadata_simple_iterator_get_block_type(const FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    return iterator->type;
}

/*@@@@add to tests*/
FLAC_API unsigned FLAC__metadata_simple_iterator_get_block_length(const FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    return iterator->length;
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_simple_iterator_get_application_id(FLAC__Metadata_SimpleIterator* iterator, FLAC__byte* id)
{
    const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);
    FLAC__ASSERT(0 != id);

    if (iterator->type != FLAC__METADATA_TYPE_APPLICATION)
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
        return false;
    }

    if (fread(id, 1, id_bytes, iterator->file) != id_bytes)
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        return false;
    }

    /* back up */
    if (0 != fseeko(iterator->file, -((int)id_bytes), SEEK_CUR))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    return true;
}

FLAC_API FLAC__StreamMetadata * FLAC__metadata_simple_iterator_get_block(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__StreamMetadata* block = FLAC__metadata_object_new(iterator->type);

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    if (0 != block)
    {
        block->is_last = iterator->is_last;
        block->length = iterator->length;

        if (!read_metadata_block_data_(iterator, block))
        {
            FLAC__metadata_object_delete(block);
            return 0;
        }

        /* back up to the beginning of the block data to stay consistent */
        if (0 != fseeko(iterator->file, iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH, SEEK_SET))
        {
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
            FLAC__metadata_object_delete(block);
            return 0;
        }
    }
    else
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    return block;
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_set_block(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, FLAC__bool use_padding)
{
    FLAC__ASSERT_DECLARATION(off_t debug_target_offset = iterator->offset[iterator->depth];)
    FLAC__bool ret;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);
    FLAC__ASSERT(0 != block);

    if (!iterator->is_writable)
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE;
        return false;
    }

    if (iterator->type == FLAC__METADATA_TYPE_STREAMINFO || block->type == FLAC__METADATA_TYPE_STREAMINFO)
    {
        if (iterator->type != block->type)
        {
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
            return false;
        }
    }

    block->is_last = iterator->is_last;

    if (iterator->length == block->length)
        return write_metadata_block_stationary_(iterator, block);
    else if (iterator->length > block->length)
    {
        if (use_padding && iterator->length >= FLAC__STREAM_METADATA_HEADER_LENGTH + block->length)
        {
            ret = write_metadata_block_stationary_with_padding_(iterator, block, iterator->length - FLAC__STREAM_METADATA_HEADER_LENGTH - block->length, block->is_last);
            FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
            FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
            return ret;
        }
        else
        {
            ret = rewrite_whole_file_(iterator, block, /*append=*/ false);
            FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
            FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
            return ret;
        }
    }
    else /* iterator->length < block->length */
    {
        unsigned padding_leftover = 0;
        FLAC__bool padding_is_last = false;
        if (use_padding)
        {
            /* first see if we can even use padding */
            if (iterator->is_last)
            {
                use_padding = false;
            }
            else
            {
                const unsigned extra_padding_bytes_required = block->length - iterator->length;
                simple_iterator_push_(iterator);
                if (!FLAC__metadata_simple_iterator_next(iterator))
                {
                    simple_iterator_pop_(iterator);
                    return false;
                }
                if (iterator->type != FLAC__METADATA_TYPE_PADDING)
                {
                    use_padding = false;
                }
                else
                {
                    if (FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length == extra_padding_bytes_required)
                    {
                        padding_leftover = 0;
                        block->is_last = iterator->is_last;
                    }
                    else if (iterator->length < extra_padding_bytes_required)
                        use_padding = false;
                    else
                    {
                        padding_leftover = FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length - extra_padding_bytes_required;
                        padding_is_last = iterator->is_last;
                        block->is_last = false;
                    }
                }
                if (!simple_iterator_pop_(iterator))
                    return false;
            }
        }
        if (use_padding)
        {
            if (padding_leftover == 0)
            {
                ret = write_metadata_block_stationary_(iterator, block);
                FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
                FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
                return ret;
            }
            else
            {
                FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
                ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
                FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
                FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
                return ret;
            }
        }
        else
        {
            ret = rewrite_whole_file_(iterator, block, /*append=*/ false);
            FLAC__ASSERT(!ret || iterator->offset[iterator->depth] == debug_target_offset);
            FLAC__ASSERT(!ret || ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
            return ret;
        }
    }
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_insert_block_after(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, FLAC__bool use_padding)
{
    unsigned padding_leftover = 0;
    FLAC__bool padding_is_last = false;

    FLAC__ASSERT_DECLARATION(off_t debug_target_offset = iterator->offset[iterator->depth] + FLAC__STREAM_METADATA_HEADER_LENGTH + iterator->length;)
    FLAC__bool ret;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);
    FLAC__ASSERT(0 != block);

    if (!iterator->is_writable)
        return false;

    if (block->type == FLAC__METADATA_TYPE_STREAMINFO)
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
        return false;
    }

    block->is_last = iterator->is_last;

    if (use_padding)
    {
        /* first see if we can even use padding */
        if (iterator->is_last)
        {
            use_padding = false;
        }
        else
        {
            simple_iterator_push_(iterator);
            if (!FLAC__metadata_simple_iterator_next(iterator))
            {
                simple_iterator_pop_(iterator);
                return false;
            }
            if (iterator->type != FLAC__METADATA_TYPE_PADDING)
            {
                use_padding = false;
            }
            else
            {
                if (iterator->length == block->length)
                {
                    padding_leftover = 0;
                    block->is_last = iterator->is_last;
                }
                else if (iterator->length < FLAC__STREAM_METADATA_HEADER_LENGTH + block->length)
                    use_padding = false;
                else
                {
                    padding_leftover = iterator->length - block->length;
                    padding_is_last = iterator->is_last;
                    block->is_last = false;
                }
            }
            if (!simple_iterator_pop_(iterator))
                return false;
        }
    }
    if (use_padding)
    {
        /* move to the next block, which is suitable padding */
        if (!FLAC__metadata_simple_iterator_next(iterator))
            return false;
        if (padding_leftover == 0)
        {
            ret = write_metadata_block_stationary_(iterator, block);
            FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
            FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
            return ret;
        }
        else
        {
            FLAC__ASSERT(padding_leftover >= FLAC__STREAM_METADATA_HEADER_LENGTH);
            ret = write_metadata_block_stationary_with_padding_(iterator, block, padding_leftover - FLAC__STREAM_METADATA_HEADER_LENGTH, padding_is_last);
            FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
            FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
            return ret;
        }
    }
    else
    {
        ret = rewrite_whole_file_(iterator, block, /*append=*/ true);
        FLAC__ASSERT(iterator->offset[iterator->depth] == debug_target_offset);
        FLAC__ASSERT(ftello(iterator->file) == debug_target_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH);
        return ret;
    }
}

FLAC_API FLAC__bool FLAC__metadata_simple_iterator_delete_block(FLAC__Metadata_SimpleIterator* iterator, FLAC__bool use_padding)
{
    FLAC__ASSERT_DECLARATION(off_t debug_target_offset = iterator->offset[iterator->depth];)
    FLAC__bool ret;

    if (iterator->type == FLAC__METADATA_TYPE_STREAMINFO)
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT;
        return false;
    }

    if (use_padding)
    {
        FLAC__StreamMetadata* padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING);
        if (0 == padding)
        {
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
            return false;
        }
        padding->length = iterator->length;
        if (!FLAC__metadata_simple_iterator_set_block(iterator, padding, false))
        {
            FLAC__metadata_object_delete(padding);
            return false;
        }
        FLAC__metadata_object_delete(padding);
        if (!FLAC__metadata_simple_iterator_prev(iterator))
            return false;
        FLAC__ASSERT(iterator->offset[iterator->depth] + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (off_t)iterator->length == debug_target_offset);
        FLAC__ASSERT(ftello(iterator->file) + (off_t)iterator->length == debug_target_offset);
        return true;
    }
    else
    {
        ret = rewrite_whole_file_(iterator, 0, /*append=*/ false);
        FLAC__ASSERT(iterator->offset[iterator->depth] + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (off_t)iterator->length == debug_target_offset);
        FLAC__ASSERT(ftello(iterator->file) + (off_t)iterator->length == debug_target_offset);
        return ret;
    }
}



/****************************************************************************
 *
 * Level 2 implementation
 *
 ***************************************************************************/


typedef struct FLAC__Metadata_Node
{
    FLAC__StreamMetadata* data;
    struct FLAC__Metadata_Node* prev, * next;
} FLAC__Metadata_Node;

struct FLAC__Metadata_Chain
{
    char* filename; /* will be nullptr if using callbacks */
    FLAC__bool is_ogg;
    FLAC__Metadata_Node* head;
    FLAC__Metadata_Node* tail;
    unsigned nodes;
    FLAC__Metadata_ChainStatus status;
    off_t first_offset, last_offset;
    /*
     * This is the length of the chain initially read from the FLAC file.
     * it is used to compare against the current length to decide whether
     * or not the whole file has to be rewritten.
     */
    off_t initial_length;
    /* @@@ hacky, these are currently only needed by ogg reader */
    FLAC__IOHandle handle;
    FLAC__IOCallback_Read read_cb;
};

struct FLAC__Metadata_Iterator
{
    FLAC__Metadata_Chain* chain;
    FLAC__Metadata_Node* current;
};

FLAC_API const char* const FLAC__Metadata_ChainStatusString[] = {
    "FLAC__METADATA_CHAIN_STATUS_OK",
    "FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT",
    "FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE",
    "FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE",
    "FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE",
    "FLAC__METADATA_CHAIN_STATUS_BAD_METADATA",
    "FLAC__METADATA_CHAIN_STATUS_READ_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR",
    "FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS",
    "FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH",
    "FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL"
};


static FLAC__Metadata_Node * node_new_()
{
    return (FLAC__Metadata_Node*)calloc(1, sizeof(FLAC__Metadata_Node));
}

static void node_delete_(FLAC__Metadata_Node* node)
{
    FLAC__ASSERT(0 != node);
    if (0 != node->data)
        FLAC__metadata_object_delete(node->data);
    free(node);
}

static void chain_init_(FLAC__Metadata_Chain* chain)
{
    FLAC__ASSERT(0 != chain);

    chain->filename = 0;
    chain->is_ogg = false;
    chain->head = chain->tail = 0;
    chain->nodes = 0;
    chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
    chain->initial_length = 0;
    chain->read_cb = 0;
}

static void chain_clear_(FLAC__Metadata_Chain* chain)
{
    FLAC__Metadata_Node* node, * next;

    FLAC__ASSERT(0 != chain);

    for (node = chain->head; node;)
    {
        next = node->next;
        node_delete_(node);
        node = next;
    }

    if (0 != chain->filename)
        free(chain->filename);

    chain_init_(chain);
}

static void chain_append_node_(FLAC__Metadata_Chain* chain, FLAC__Metadata_Node* node)
{
    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != node);
    FLAC__ASSERT(0 != node->data);

    node->next = node->prev = 0;
    node->data->is_last = true;
    if (0 != chain->tail)
        chain->tail->data->is_last = false;

    if (0 == chain->head)
        chain->head = node;
    else
    {
        FLAC__ASSERT(0 != chain->tail);
        chain->tail->next = node;
        node->prev = chain->tail;
    }
    chain->tail = node;
    chain->nodes++;
}

static void chain_remove_node_(FLAC__Metadata_Chain* chain, FLAC__Metadata_Node* node)
{
    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != node);

    if (node == chain->head)
        chain->head = node->next;
    else
        node->prev->next = node->next;

    if (node == chain->tail)
        chain->tail = node->prev;
    else
        node->next->prev = node->prev;

    if (0 != chain->tail)
        chain->tail->data->is_last = true;

    chain->nodes--;
}

static void chain_delete_node_(FLAC__Metadata_Chain* chain, FLAC__Metadata_Node* node)
{
    chain_remove_node_(chain, node);
    node_delete_(node);
}

static off_t chain_calculate_length_(FLAC__Metadata_Chain* chain)
{
    const FLAC__Metadata_Node* node;
    off_t length = 0;
    for (node = chain->head; node; node = node->next)
        length += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
    return length;
}

static void iterator_insert_node_(FLAC__Metadata_Iterator* iterator, FLAC__Metadata_Node* node)
{
    FLAC__ASSERT(0 != node);
    FLAC__ASSERT(0 != node->data);
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);
    FLAC__ASSERT(0 != iterator->chain);
    FLAC__ASSERT(0 != iterator->chain->head);
    FLAC__ASSERT(0 != iterator->chain->tail);

    node->data->is_last = false;

    node->prev = iterator->current->prev;
    node->next = iterator->current;

    if (0 == node->prev)
        iterator->chain->head = node;
    else
        node->prev->next = node;

    iterator->current->prev = node;

    iterator->chain->nodes++;
}

static void iterator_insert_node_after_(FLAC__Metadata_Iterator* iterator, FLAC__Metadata_Node* node)
{
    FLAC__ASSERT(0 != node);
    FLAC__ASSERT(0 != node->data);
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);
    FLAC__ASSERT(0 != iterator->chain);
    FLAC__ASSERT(0 != iterator->chain->head);
    FLAC__ASSERT(0 != iterator->chain->tail);

    iterator->current->data->is_last = false;

    node->prev = iterator->current;
    node->next = iterator->current->next;

    if (0 == node->next)
        iterator->chain->tail = node;
    else
        node->next->prev = node;

    node->prev->next = node;

    iterator->chain->tail->data->is_last = true;

    iterator->chain->nodes++;
}

/* return true iff node and node->next are both padding */
static FLAC__bool chain_merge_adjacent_padding_(FLAC__Metadata_Chain* chain, FLAC__Metadata_Node* node)
{
    if (node->data->type == FLAC__METADATA_TYPE_PADDING && 0 != node->next && node->next->data->type == FLAC__METADATA_TYPE_PADDING)
    {
        const unsigned growth = FLAC__STREAM_METADATA_HEADER_LENGTH + node->next->data->length;
        node->data->length += growth;

        chain_delete_node_(chain, node->next);
        return true;
    }
    else
        return false;
}

/* Returns the new length of the chain, or 0 if there was an error. */
/* WATCHOUT: This can get called multiple times before a write, so
 * it should still work when this happens.
 */
/* WATCHOUT: Make sure to also update the logic in
 * FLAC__metadata_chain_check_if_tempfile_needed() if the logic here changes.
 */
static off_t chain_prepare_for_write_(FLAC__Metadata_Chain* chain, FLAC__bool use_padding)
{
    off_t current_length = chain_calculate_length_(chain);

    if (use_padding)
    {
        /* if the metadata shrank and the last block is padding, we just extend the last padding block */
        if (current_length < chain->initial_length && chain->tail->data->type == FLAC__METADATA_TYPE_PADDING)
        {
            const off_t delta = chain->initial_length - current_length;
            chain->tail->data->length += delta;
            current_length += delta;
            FLAC__ASSERT(current_length == chain->initial_length);
        }
        /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
        else if (current_length + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length)
        {
            FLAC__StreamMetadata* padding;
            FLAC__Metadata_Node* node;
            if (0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING)))
            {
                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
                return 0;
            }
            padding->length = chain->initial_length - (FLAC__STREAM_METADATA_HEADER_LENGTH + current_length);
            if (0 == (node = node_new_()))
            {
                FLAC__metadata_object_delete(padding);
                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
                return 0;
            }
            node->data = padding;
            chain_append_node_(chain, node);
            current_length = chain_calculate_length_(chain);
            FLAC__ASSERT(current_length == chain->initial_length);
        }
        /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
        else if (current_length > chain->initial_length)
        {
            const off_t delta = current_length - chain->initial_length;
            if (chain->tail->data->type == FLAC__METADATA_TYPE_PADDING)
            {
                /* if the delta is exactly the size of the last padding block, remove the padding block */
                if ((off_t)chain->tail->data->length + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta)
                {
                    chain_delete_node_(chain, chain->tail);
                    current_length = chain_calculate_length_(chain);
                    FLAC__ASSERT(current_length == chain->initial_length);
                }
                /* if there is at least 'delta' bytes of padding, trim the padding down */
                else if ((off_t)chain->tail->data->length >= delta)
                {
                    chain->tail->data->length -= delta;
                    current_length -= delta;
                    FLAC__ASSERT(current_length == chain->initial_length);
                }
            }
        }
    }

    return current_length;
}

static FLAC__bool chain_read_cb_(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Tell tell_cb)
{
    FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != chain);

    /* we assume we're already at the beginning of the file */

    switch (seek_to_first_metadata_block_cb_(handle, read_cb, seek_cb))
    {
        case 0:
            break;
        case 1:
            chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
            return false;
        case 2:
            chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
            return false;
        case 3:
            chain->status = FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
            return false;
        default:
            FLAC__ASSERT(0);
            return false;
    }

    {
        FLAC__int64 pos = tell_cb(handle);
        if (pos < 0)
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
            return false;
        }
        chain->first_offset = (off_t)pos;
    }

    {
        FLAC__bool is_last;
        FLAC__MetadataType type;
        unsigned length;

        do
        {
            node = node_new_();
            if (0 == node)
            {
                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
                return false;
            }

            if (!read_metadata_block_header_cb_(handle, read_cb, &is_last, &type, &length))
            {
                chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
                return false;
            }

            node->data = FLAC__metadata_object_new(type);
            if (0 == node->data)
            {
                node_delete_(node);
                chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
                return false;
            }

            node->data->is_last = is_last;
            node->data->length = length;

            chain->status = get_equivalent_status_(read_metadata_block_data_cb_(handle, read_cb, seek_cb, node->data));
            if (chain->status != FLAC__METADATA_CHAIN_STATUS_OK)
            {
                node_delete_(node);
                return false;
            }
            chain_append_node_(chain, node);
        }
        while (!is_last);
    }

    {
        FLAC__int64 pos = tell_cb(handle);
        if (pos < 0)
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
            return false;
        }
        chain->last_offset = (off_t)pos;
    }

    chain->initial_length = chain_calculate_length_(chain);

    return true;
}

static FLAC__StreamDecoderReadStatus chain_read_ogg_read_cb_(const FLAC__StreamDecoder* decoder, FLAC__byte buffer[], size_t* bytes, void* client_data)
{
    FLAC__Metadata_Chain* chain = (FLAC__Metadata_Chain*)client_data;
    decoder;
    if (*bytes > 0 && chain->status == FLAC__METADATA_CHAIN_STATUS_OK)
    {
        *bytes = chain->read_cb(buffer, sizeof(FLAC__byte), *bytes, chain->handle);
        if (*bytes == 0)
            return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
        else
            return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
    }
    else
        return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
}

static FLAC__StreamDecoderWriteStatus chain_read_ogg_write_cb_(const FLAC__StreamDecoder* decoder, const FLAC__Frame* frame, const FLAC__int32* const buffer[], void* client_data)
{
    decoder, frame, buffer, client_data;
    return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;
}

static void chain_read_ogg_metadata_cb_(const FLAC__StreamDecoder* decoder, const FLAC__StreamMetadata* metadata, void* client_data)
{
    FLAC__Metadata_Chain* chain = (FLAC__Metadata_Chain*)client_data;
    FLAC__Metadata_Node* node;

    decoder;

    node = node_new_();
    if (0 == node)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return;
    }

    node->data = FLAC__metadata_object_clone(metadata);
    if (0 == node->data)
    {
        node_delete_(node);
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return;
    }

    chain_append_node_(chain, node);
}

static void chain_read_ogg_error_cb_(const FLAC__StreamDecoder* decoder, FLAC__StreamDecoderErrorStatus status, void* client_data)
{
    FLAC__Metadata_Chain* chain = (FLAC__Metadata_Chain*)client_data;
    decoder, status;
    chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
}

static FLAC__bool chain_read_ogg_cb_(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb)
{
    FLAC__StreamDecoder* decoder;

    FLAC__ASSERT(0 != chain);

    /* we assume we're already at the beginning of the file */

    chain->handle = handle;
    chain->read_cb = read_cb;
    if (0 == (decoder = FLAC__stream_decoder_new()))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
    }
    FLAC__stream_decoder_set_metadata_respond_all(decoder);
    if (FLAC__stream_decoder_init_ogg_stream(decoder, chain_read_ogg_read_cb_, /*seek_callback=*/ 0, /*tell_callback=*/ 0, /*length_callback=*/ 0, /*eof_callback=*/ 0, chain_read_ogg_write_cb_, chain_read_ogg_metadata_cb_, chain_read_ogg_error_cb_, chain) != FLAC__STREAM_DECODER_INIT_STATUS_OK)
    {
        FLAC__stream_decoder_delete(decoder);
        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
        return false;
    }

    chain->first_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */

    if (!FLAC__stream_decoder_process_until_end_of_metadata(decoder))
        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR; /*@@@ maybe needs better error code */
    if (chain->status != FLAC__METADATA_CHAIN_STATUS_OK)
    {
        FLAC__stream_decoder_delete(decoder);
        return false;
    }

    FLAC__stream_decoder_delete(decoder);

    chain->last_offset = 0; /*@@@ wrong; will need to be set correctly to implement metadata writing for Ogg FLAC */

    chain->initial_length = chain_calculate_length_(chain);

    return true;
}

static FLAC__bool chain_rewrite_metadata_in_place_cb_(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, FLAC__IOCallback_Seek seek_cb)
{
    FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != chain->head);

    if (0 != seek_cb(handle, chain->first_offset, SEEK_SET))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        return false;
    }

    for (node = chain->head; node; node = node->next)
    {
        if (!write_metadata_block_header_cb_(handle, write_cb, node->data))
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
            return false;
        }
        if (!write_metadata_block_data_cb_(handle, write_cb, node->data))
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
            return false;
        }
    }

    /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

    chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
    return true;
}

static FLAC__bool chain_rewrite_metadata_in_place_(FLAC__Metadata_Chain* chain)
{
    FILE* file;
    FLAC__bool ret;

    FLAC__ASSERT(0 != chain->filename);

    if (0 == (file = fopen(chain->filename, "r+b")))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
        return false;
    }

    /* chain_rewrite_metadata_in_place_cb_() sets chain->status for us */
    ret = chain_rewrite_metadata_in_place_cb_(chain, (FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, fseek_wrapper_);

    fclose(file);

    return ret;
}

static FLAC__bool chain_rewrite_file_(FLAC__Metadata_Chain* chain, const char* tempfile_path_prefix)
{
    FILE* f, * tempfile;
    char* tempfilename;
    FLAC__Metadata_SimpleIteratorStatus status;
    const FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != chain->filename);
    FLAC__ASSERT(0 != chain->head);

    /* copy the file prefix (data up to first metadata block */
    if (0 == (f = fopen(chain->filename, "rb")))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
        return false;
    }
    if (!open_tempfile_(chain->filename, tempfile_path_prefix, &tempfile, &tempfilename, &status))
    {
        chain->status = get_equivalent_status_(status);
        cleanup_tempfile_(&tempfile, &tempfilename);
        return false;
    }
    if (!copy_n_bytes_from_file_(f, tempfile, chain->first_offset, &status))
    {
        chain->status = get_equivalent_status_(status);
        cleanup_tempfile_(&tempfile, &tempfilename);
        return false;
    }

    /* write the metadata */
    for (node = chain->head; node; node = node->next)
    {
        if (!write_metadata_block_header_(tempfile, &status, node->data))
        {
            chain->status = get_equivalent_status_(status);
            return false;
        }
        if (!write_metadata_block_data_(tempfile, &status, node->data))
        {
            chain->status = get_equivalent_status_(status);
            return false;
        }
    }
    /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

    /* copy the file postfix (everything after the metadata) */
    if (0 != fseeko(f, chain->last_offset, SEEK_SET))
    {
        cleanup_tempfile_(&tempfile, &tempfilename);
        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        return false;
    }
    if (!copy_remaining_bytes_from_file_(f, tempfile, &status))
    {
        cleanup_tempfile_(&tempfile, &tempfilename);
        chain->status = get_equivalent_status_(status);
        return false;
    }

    /* move the tempfile on top of the original */
    fclose(f);
    if (!transport_tempfile_(chain->filename, &tempfile, &tempfilename, &status))
        return false;

    return true;
}

/* assumes 'handle' is already at beginning of file */
static FLAC__bool chain_rewrite_file_cb_(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb)
{
    FLAC__Metadata_SimpleIteratorStatus status;
    const FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 == chain->filename);
    FLAC__ASSERT(0 != chain->head);

    /* copy the file prefix (data up to first metadata block */
    if (!copy_n_bytes_from_file_cb_(handle, read_cb, temp_handle, temp_write_cb, chain->first_offset, &status))
    {
        chain->status = get_equivalent_status_(status);
        return false;
    }

    /* write the metadata */
    for (node = chain->head; node; node = node->next)
    {
        if (!write_metadata_block_header_cb_(temp_handle, temp_write_cb, node->data))
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
            return false;
        }
        if (!write_metadata_block_data_cb_(temp_handle, temp_write_cb, node->data))
        {
            chain->status = FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
            return false;
        }
    }
    /*FLAC__ASSERT(fflush(), ftello() == chain->last_offset);*/

    /* copy the file postfix (everything after the metadata) */
    if (0 != seek_cb(handle, chain->last_offset, SEEK_SET))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        return false;
    }
    if (!copy_remaining_bytes_from_file_cb_(handle, read_cb, eof_cb, temp_handle, temp_write_cb, &status))
    {
        chain->status = get_equivalent_status_(status);
        return false;
    }

    return true;
}

FLAC_API FLAC__Metadata_Chain * FLAC__metadata_chain_new()
{
    FLAC__Metadata_Chain* chain = (FLAC__Metadata_Chain*)calloc(1, sizeof(FLAC__Metadata_Chain));

    if (0 != chain)
        chain_init_(chain);

    return chain;
}

FLAC_API void FLAC__metadata_chain_delete(FLAC__Metadata_Chain* chain)
{
    FLAC__ASSERT(0 != chain);

    chain_clear_(chain);

    free(chain);
}

FLAC_API FLAC__Metadata_ChainStatus FLAC__metadata_chain_status(FLAC__Metadata_Chain* chain)
{
    FLAC__Metadata_ChainStatus status;

    FLAC__ASSERT(0 != chain);

    status = chain->status;
    chain->status = FLAC__METADATA_CHAIN_STATUS_OK;
    return status;
}

static FLAC__bool chain_read_(FLAC__Metadata_Chain* chain, const char* filename, FLAC__bool is_ogg)
{
    FILE* file;
    FLAC__bool ret;

    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != filename);

    chain_clear_(chain);

    if (0 == (chain->filename = _strdup(filename)))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        return false;
    }

    chain->is_ogg = is_ogg;

    if (0 == (file = fopen(filename, "rb")))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
        return false;
    }

    /* the function also sets chain->status for us */
    ret = is_ogg ?
          chain_read_ogg_cb_(chain, file, (FLAC__IOCallback_Read)fread) :
          chain_read_cb_(chain, file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, ftell_wrapper_)
    ;

    fclose(file);

    return ret;
}

FLAC_API FLAC__bool FLAC__metadata_chain_read(FLAC__Metadata_Chain* chain, const char* filename)
{
    return chain_read_(chain, filename, /*is_ogg=*/ false);
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg(FLAC__Metadata_Chain* chain, const char* filename)
{
    return chain_read_(chain, filename, /*is_ogg=*/ true);
}

static FLAC__bool chain_read_with_callbacks_(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__bool is_ogg)
{
    FLAC__bool ret;

    FLAC__ASSERT(0 != chain);

    chain_clear_(chain);

    if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.tell)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
        return false;
    }

    chain->is_ogg = is_ogg;

    /* rewind */
    if (0 != callbacks.seek(handle, 0, SEEK_SET))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        return false;
    }

    /* the function also sets chain->status for us */
    ret = is_ogg ?
          chain_read_ogg_cb_(chain, handle, callbacks.read) :
          chain_read_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.tell)
    ;

    return ret;
}

FLAC_API FLAC__bool FLAC__metadata_chain_read_with_callbacks(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
    return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/ false);
}

/*@@@@add to tests*/
FLAC_API FLAC__bool FLAC__metadata_chain_read_ogg_with_callbacks(FLAC__Metadata_Chain* chain, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
    return chain_read_with_callbacks_(chain, handle, callbacks, /*is_ogg=*/ true);
}

FLAC_API FLAC__bool FLAC__metadata_chain_check_if_tempfile_needed(FLAC__Metadata_Chain* chain, FLAC__bool use_padding)
{
    /* This does all the same checks that are in chain_prepare_for_write_()
     * but doesn't actually alter the chain.  Make sure to update the logic
     * here if chain_prepare_for_write_() changes.
     */
    const off_t current_length = chain_calculate_length_(chain);

    FLAC__ASSERT(0 != chain);

    if (use_padding)
    {
        /* if the metadata shrank and the last block is padding, we just extend the last padding block */
        if (current_length < chain->initial_length && chain->tail->data->type == FLAC__METADATA_TYPE_PADDING)
            return false;
        /* if the metadata shrank more than 4 bytes then there's room to add another padding block */
        else if (current_length + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH <= chain->initial_length)
            return false;
        /* if the metadata grew but the last block is padding, try cutting the padding to restore the original length so we don't have to rewrite the whole file */
        else if (current_length > chain->initial_length)
        {
            const off_t delta = current_length - chain->initial_length;
            if (chain->tail->data->type == FLAC__METADATA_TYPE_PADDING)
            {
                /* if the delta is exactly the size of the last padding block, remove the padding block */
                if ((off_t)chain->tail->data->length + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH == delta)
                    return false;
                /* if there is at least 'delta' bytes of padding, trim the padding down */
                else if ((off_t)chain->tail->data->length >= delta)
                    return false;
            }
        }
    }

    return (current_length != chain->initial_length);
}

FLAC_API FLAC__bool FLAC__metadata_chain_write(FLAC__Metadata_Chain* chain, FLAC__bool use_padding, FLAC__bool preserve_file_stats)
{
    struct stat stats;
    const char* tempfile_path_prefix = 0;
    off_t current_length;

    FLAC__ASSERT(0 != chain);

    if (chain->is_ogg)   /* cannot write back to Ogg FLAC yet */
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
        return false;
    }

    if (0 == chain->filename)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
        return false;
    }

    current_length = chain_prepare_for_write_(chain, use_padding);

    /* a return value of 0 means there was an error; chain->status is already set */
    if (0 == current_length)
        return false;

    if (preserve_file_stats)
        get_file_stats_(chain->filename, &stats);

    if (current_length == chain->initial_length)
    {
        if (!chain_rewrite_metadata_in_place_(chain))
            return false;
    }
    else
    {
        if (!chain_rewrite_file_(chain, tempfile_path_prefix))
            return false;

        /* recompute lengths and offsets */
        {
            const FLAC__Metadata_Node* node;
            chain->initial_length = current_length;
            chain->last_offset = chain->first_offset;
            for (node = chain->head; node; node = node->next)
                chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
        }
    }

    if (preserve_file_stats)
        set_file_stats_(chain->filename, &stats);

    return true;
}

FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks(FLAC__Metadata_Chain* chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks)
{
    off_t current_length;

    FLAC__ASSERT(0 != chain);

    if (chain->is_ogg)   /* cannot write back to Ogg FLAC yet */
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
        return false;
    }

    if (0 != chain->filename)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
        return false;
    }

    if (0 == callbacks.write || 0 == callbacks.seek)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
        return false;
    }

    if (FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
        return false;
    }

    current_length = chain_prepare_for_write_(chain, use_padding);

    /* a return value of 0 means there was an error; chain->status is already set */
    if (0 == current_length)
        return false;

    FLAC__ASSERT(current_length == chain->initial_length);

    return chain_rewrite_metadata_in_place_cb_(chain, handle, callbacks.write, callbacks.seek);
}

FLAC_API FLAC__bool FLAC__metadata_chain_write_with_callbacks_and_tempfile(FLAC__Metadata_Chain* chain, FLAC__bool use_padding, FLAC__IOHandle handle, FLAC__IOCallbacks callbacks, FLAC__IOHandle temp_handle, FLAC__IOCallbacks temp_callbacks)
{
    off_t current_length;

    FLAC__ASSERT(0 != chain);

    if (chain->is_ogg)   /* cannot write back to Ogg FLAC yet */
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
        return false;
    }

    if (0 != chain->filename)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_READ_WRITE_MISMATCH;
        return false;
    }

    if (0 == callbacks.read || 0 == callbacks.seek || 0 == callbacks.eof)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
        return false;
    }
    if (0 == temp_callbacks.write)
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_INVALID_CALLBACKS;
        return false;
    }

    if (!FLAC__metadata_chain_check_if_tempfile_needed(chain, use_padding))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_WRONG_WRITE_CALL;
        return false;
    }

    current_length = chain_prepare_for_write_(chain, use_padding);

    /* a return value of 0 means there was an error; chain->status is already set */
    if (0 == current_length)
        return false;

    FLAC__ASSERT(current_length != chain->initial_length);

    /* rewind */
    if (0 != callbacks.seek(handle, 0, SEEK_SET))
    {
        chain->status = FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        return false;
    }

    if (!chain_rewrite_file_cb_(chain, handle, callbacks.read, callbacks.seek, callbacks.eof, temp_handle, temp_callbacks.write))
        return false;

    /* recompute lengths and offsets */
    {
        const FLAC__Metadata_Node* node;
        chain->initial_length = current_length;
        chain->last_offset = chain->first_offset;
        for (node = chain->head; node; node = node->next)
            chain->last_offset += (FLAC__STREAM_METADATA_HEADER_LENGTH + node->data->length);
    }

    return true;
}

FLAC_API void FLAC__metadata_chain_merge_padding(FLAC__Metadata_Chain* chain)
{
    FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != chain);

    for (node = chain->head; node;)
    {
        if (!chain_merge_adjacent_padding_(chain, node))
            node = node->next;
    }
}

FLAC_API void FLAC__metadata_chain_sort_padding(FLAC__Metadata_Chain* chain)
{
    FLAC__Metadata_Node* node, * save;
    unsigned i;

    FLAC__ASSERT(0 != chain);

    /*
     * Don't try and be too smart... this simple algo is good enough for
     * the small number of nodes that we deal with.
     */
    for (i = 0, node = chain->head; i < chain->nodes; i++)
    {
        if (node->data->type == FLAC__METADATA_TYPE_PADDING)
        {
            save = node->next;
            chain_remove_node_(chain, node);
            chain_append_node_(chain, node);
            node = save;
        }
        else
        {
            node = node->next;
        }
    }

    FLAC__metadata_chain_merge_padding(chain);
}


FLAC_API FLAC__Metadata_Iterator * FLAC__metadata_iterator_new()
{
    FLAC__Metadata_Iterator* iterator = (FLAC__Metadata_Iterator*)calloc(1, sizeof(FLAC__Metadata_Iterator));

    /* calloc() implies:
        iterator->current = 0;
        iterator->chain = 0;
     */

    return iterator;
}

FLAC_API void FLAC__metadata_iterator_delete(FLAC__Metadata_Iterator* iterator)
{
    FLAC__ASSERT(0 != iterator);

    free(iterator);
}

FLAC_API void FLAC__metadata_iterator_init(FLAC__Metadata_Iterator* iterator, FLAC__Metadata_Chain* chain)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != chain);
    FLAC__ASSERT(0 != chain->head);

    iterator->chain = chain;
    iterator->current = chain->head;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_next(FLAC__Metadata_Iterator* iterator)
{
    FLAC__ASSERT(0 != iterator);

    if (0 == iterator->current || 0 == iterator->current->next)
        return false;

    iterator->current = iterator->current->next;
    return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_prev(FLAC__Metadata_Iterator* iterator)
{
    FLAC__ASSERT(0 != iterator);

    if (0 == iterator->current || 0 == iterator->current->prev)
        return false;

    iterator->current = iterator->current->prev;
    return true;
}

FLAC_API FLAC__MetadataType FLAC__metadata_iterator_get_block_type(const FLAC__Metadata_Iterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);
    FLAC__ASSERT(0 != iterator->current->data);

    return iterator->current->data->type;
}

FLAC_API FLAC__StreamMetadata * FLAC__metadata_iterator_get_block(FLAC__Metadata_Iterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);

    return iterator->current->data;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_set_block(FLAC__Metadata_Iterator* iterator, FLAC__StreamMetadata* block)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != block);
    return FLAC__metadata_iterator_delete_block(iterator, false) && FLAC__metadata_iterator_insert_block_after(iterator, block);
}

FLAC_API FLAC__bool FLAC__metadata_iterator_delete_block(FLAC__Metadata_Iterator* iterator, FLAC__bool replace_with_padding)
{
    FLAC__Metadata_Node* save;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);

    if (0 == iterator->current->prev)
    {
        FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
        return false;
    }

    save = iterator->current->prev;

    if (replace_with_padding)
    {
        FLAC__metadata_object_delete_data(iterator->current->data);
        iterator->current->data->type = FLAC__METADATA_TYPE_PADDING;
    }
    else
    {
        chain_delete_node_(iterator->chain, iterator->current);
    }

    iterator->current = save;
    return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_before(FLAC__Metadata_Iterator* iterator, FLAC__StreamMetadata* block)
{
    FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);
    FLAC__ASSERT(0 != block);

    if (block->type == FLAC__METADATA_TYPE_STREAMINFO)
        return false;

    if (0 == iterator->current->prev)
    {
        FLAC__ASSERT(iterator->current->data->type == FLAC__METADATA_TYPE_STREAMINFO);
        return false;
    }

    if (0 == (node = node_new_()))
        return false;

    node->data = block;
    iterator_insert_node_(iterator, node);
    iterator->current = node;
    return true;
}

FLAC_API FLAC__bool FLAC__metadata_iterator_insert_block_after(FLAC__Metadata_Iterator* iterator, FLAC__StreamMetadata* block)
{
    FLAC__Metadata_Node* node;

    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->current);
    FLAC__ASSERT(0 != block);

    if (block->type == FLAC__METADATA_TYPE_STREAMINFO)
        return false;

    if (0 == (node = node_new_()))
        return false;

    node->data = block;
    iterator_insert_node_after_(iterator, node);
    iterator->current = node;
    return true;
}


/****************************************************************************
 *
 * Local function definitions
 *
 ***************************************************************************/

void pack_uint32_(FLAC__uint32 val, FLAC__byte* b, unsigned bytes)
{
    unsigned i;

    b += bytes;

    for (i = 0; i < bytes; i++)
    {
        *(--b) = (FLAC__byte)(val & 0xff);
        val >>= 8;
    }
}

void pack_uint32_little_endian_(FLAC__uint32 val, FLAC__byte* b, unsigned bytes)
{
    unsigned i;

    for (i = 0; i < bytes; i++)
    {
        *(b++) = (FLAC__byte)(val & 0xff);
        val >>= 8;
    }
}

void pack_uint64_(FLAC__uint64 val, FLAC__byte* b, unsigned bytes)
{
    unsigned i;

    b += bytes;

    for (i = 0; i < bytes; i++)
    {
        *(--b) = (FLAC__byte)(val & 0xff);
        val >>= 8;
    }
}

FLAC__uint32 unpack_uint32_(FLAC__byte* b, unsigned bytes)
{
    FLAC__uint32 ret = 0;
    unsigned i;

    for (i = 0; i < bytes; i++)
        ret = (ret << 8) | (FLAC__uint32)(*b++);

    return ret;
}

FLAC__uint32 unpack_uint32_little_endian_(FLAC__byte* b, unsigned bytes)
{
    FLAC__uint32 ret = 0;
    unsigned i;

    b += bytes;

    for (i = 0; i < bytes; i++)
        ret = (ret << 8) | (FLAC__uint32)(*--b);

    return ret;
}

FLAC__uint64 unpack_uint64_(FLAC__byte* b, unsigned bytes)
{
    FLAC__uint64 ret = 0;
    unsigned i;

    for (i = 0; i < bytes; i++)
        ret = (ret << 8) | (FLAC__uint64)(*b++);

    return ret;
}

FLAC__bool read_metadata_block_header_(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    if (!read_metadata_block_header_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, &iterator->is_last, &iterator->type, &iterator->length))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        return false;
    }

    return true;
}

FLAC__bool read_metadata_block_data_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block)
{
    FLAC__ASSERT(0 != iterator);
    FLAC__ASSERT(0 != iterator->file);

    iterator->status = read_metadata_block_data_cb_((FLAC__IOHandle)iterator->file, (FLAC__IOCallback_Read)fread, fseek_wrapper_, block);

    return (iterator->status == FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK);
}

FLAC__bool read_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__bool* is_last, FLAC__MetadataType* type, unsigned* length)
{
    FLAC__byte raw_header[FLAC__STREAM_METADATA_HEADER_LENGTH];

    if (read_cb(raw_header, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
        return false;

    *is_last = raw_header[0] & 0x80 ? true : false;
    *type = (FLAC__MetadataType)(raw_header[0] & 0x7f);
    *length = unpack_uint32_(raw_header + 1, 3);

    /* Note that we don't check:
     *    if(iterator->type >= FLAC__METADATA_TYPE_UNDEFINED)
     * we just will read in an opaque block
     */

    return true;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata* block)
{
    switch (block->type)
    {
        case FLAC__METADATA_TYPE_STREAMINFO:
            return read_metadata_block_data_streaminfo_cb_(handle, read_cb, &block->data.stream_info);
        case FLAC__METADATA_TYPE_PADDING:
            return read_metadata_block_data_padding_cb_(handle, seek_cb, &block->data.padding, block->length);
        case FLAC__METADATA_TYPE_APPLICATION:
            return read_metadata_block_data_application_cb_(handle, read_cb, &block->data.application, block->length);
        case FLAC__METADATA_TYPE_SEEKTABLE:
            return read_metadata_block_data_seektable_cb_(handle, read_cb, &block->data.seek_table, block->length);
        case FLAC__METADATA_TYPE_VORBIS_COMMENT:
            return read_metadata_block_data_vorbis_comment_cb_(handle, read_cb, &block->data.vorbis_comment);
        case FLAC__METADATA_TYPE_CUESHEET:
            return read_metadata_block_data_cuesheet_cb_(handle, read_cb, &block->data.cue_sheet);
        case FLAC__METADATA_TYPE_PICTURE:
            return read_metadata_block_data_picture_cb_(handle, read_cb, &block->data.picture);
        default:
            return read_metadata_block_data_unknown_cb_(handle, read_cb, &block->data.unknown, block->length);
    }
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_StreamInfo* block)
{
    FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH], * b;

    if (read_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

    b = buffer;

    /* we are using hardcoded numbers for simplicity but we should
     * probably eventually write a bit-level unpacker and use the
     * _STREAMINFO_ constants.
     */
    block->min_blocksize = unpack_uint32_(b, 2); b += 2;
    block->max_blocksize = unpack_uint32_(b, 2); b += 2;
    block->min_framesize = unpack_uint32_(b, 3); b += 3;
    block->max_framesize = unpack_uint32_(b, 3); b += 3;
    block->sample_rate = (unpack_uint32_(b, 2) << 4) | ((unsigned)(b[2] & 0xf0) >> 4);
    block->channels = (unsigned)((b[2] & 0x0e) >> 1) + 1;
    block->bits_per_sample = ((((unsigned)(b[2] & 0x01)) << 4) | (((unsigned)(b[3] & 0xf0)) >> 4)) + 1;
    block->total_samples = (((FLAC__uint64)(b[3] & 0x0f)) << 32) | unpack_uint64_(b + 4, 4);
    memcpy(block->md5sum, b + 8, 16);

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Seek seek_cb, FLAC__StreamMetadata_Padding* block, unsigned block_length)
{
    block; /* nothing to do; we don't care about reading the padding bytes */

    if (0 != seek_cb(handle, block_length, SEEK_CUR))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Application* block, unsigned block_length)
{
    const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

    if (read_cb(block->id, 1, id_bytes, handle) != id_bytes)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

    if (block_length < id_bytes)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

    block_length -= id_bytes;

    if (block_length == 0)
    {
        block->data = 0;
    }
    else
    {
        if (0 == (block->data = (FLAC__byte*)malloc(block_length)))
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

        if (read_cb(block->data, 1, block_length, handle) != block_length)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_SeekTable* block, unsigned block_length)
{
    unsigned i;
    FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];

    FLAC__ASSERT(block_length % FLAC__STREAM_METADATA_SEEKPOINT_LENGTH == 0);

    block->num_points = block_length / FLAC__STREAM_METADATA_SEEKPOINT_LENGTH;

    if (block->num_points == 0)
        block->points = 0;
    else if (0 == (block->points = (FLAC__StreamMetadata_SeekPoint*)safe_malloc_mul_2op_(block->num_points, /*times*/ sizeof(FLAC__StreamMetadata_SeekPoint))))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    for (i = 0; i < block->num_points; i++)
    {
        if (read_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        /* some MAGIC NUMBERs here */
        block->points[i].sample_number = unpack_uint64_(buffer, 8);
        block->points[i].stream_offset = unpack_uint64_(buffer + 8, 8);
        block->points[i].frame_samples = unpack_uint32_(buffer + 16, 2);
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_entry_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment_Entry* entry)
{
    const unsigned entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
    FLAC__byte buffer[4]; /* magic number is asserted below */

    FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8 == sizeof(buffer));

    if (read_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    entry->length = unpack_uint32_little_endian_(buffer, entry_length_len);

    if (0 != entry->entry)
        free(entry->entry);

    if (entry->length == 0)
    {
        entry->entry = 0;
    }
    else
    {
        if (0 == (entry->entry = (FLAC__byte*)safe_malloc_add_2op_(entry->length, /*+*/ 1)))
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

        if (read_cb(entry->entry, 1, entry->length, handle) != entry->length)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

        entry->entry[entry->length] = '\0';
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_VorbisComment* block)
{
    unsigned i;
    FLAC__Metadata_SimpleIteratorStatus status;
    const unsigned num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
    FLAC__byte buffer[4]; /* magic number is asserted below */

    FLAC__ASSERT(FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8 == sizeof(buffer));

    if (FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, &(block->vendor_string))))
        return status;

    if (read_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->num_comments = unpack_uint32_little_endian_(buffer, num_comments_len);

    if (block->num_comments == 0)
    {
        block->comments = 0;
    }
    else if (0 == (block->comments = (FLAC__StreamMetadata_VorbisComment_Entry*)calloc(block->num_comments, sizeof(FLAC__StreamMetadata_VorbisComment_Entry))))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    for (i = 0; i < block->num_comments; i++)
    {
        if (FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = read_metadata_block_data_vorbis_comment_entry_cb_(handle, read_cb, block->comments + i)))
            return status;
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_track_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet_Track* track)
{
    unsigned i, len;
    FLAC__byte buffer[32]; /* asserted below that this is big enough */

    FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    track->offset = unpack_uint64_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    track->number = (FLAC__byte)unpack_uint32_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
    if (read_cb(track->isrc, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

    FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
    len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN == 1);
    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN == 1);
    track->type = buffer[0] >> 7;
    track->pre_emphasis = (buffer[0] >> 6) & 1;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    track->num_indices = (FLAC__byte)unpack_uint32_(buffer, len);

    if (track->num_indices == 0)
    {
        track->indices = 0;
    }
    else if (0 == (track->indices = (FLAC__StreamMetadata_CueSheet_Index*)calloc(track->num_indices, sizeof(FLAC__StreamMetadata_CueSheet_Index))))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    for (i = 0; i < track->num_indices; i++)
    {
        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
        if (read_cb(buffer, 1, len, handle) != len)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        track->indices[i].offset = unpack_uint64_(buffer, len);

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
        if (read_cb(buffer, 1, len, handle) != len)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
        track->indices[i].number = (FLAC__byte)unpack_uint32_(buffer, len);

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
        if (read_cb(buffer, 1, len, handle) != len)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_CueSheet* block)
{
    unsigned i, len;
    FLAC__Metadata_SimpleIteratorStatus status;
    FLAC__byte buffer[1024]; /* MSVC needs a constant expression so we put a magic number and assert */

    FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8 <= sizeof(buffer));
    FLAC__ASSERT(sizeof(FLAC__uint64) <= sizeof(buffer));

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
    if (read_cb(block->media_catalog_number, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->lead_in = unpack_uint64_(buffer, len);

    FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
    len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->is_cd = buffer[0] & 0x80 ? true : false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->num_tracks = unpack_uint32_(buffer, len);

    if (block->num_tracks == 0)
    {
        block->tracks = 0;
    }
    else if (0 == (block->tracks = (FLAC__StreamMetadata_CueSheet_Track*)calloc(block->num_tracks, sizeof(FLAC__StreamMetadata_CueSheet_Track))))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    for (i = 0; i < block->num_tracks; i++)
    {
        if (FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK != (status = read_metadata_block_data_cuesheet_track_cb_(handle, read_cb, block->tracks + i)))
            return status;
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

static FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cstring_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__byte** data, FLAC__uint32* length, FLAC__uint32 length_len)
{
    FLAC__byte buffer[sizeof(FLAC__uint32)];

    FLAC__ASSERT(0 != data);
    FLAC__ASSERT(length_len % 8 == 0);

    length_len /= 8; /* convert to bytes */

    FLAC__ASSERT(sizeof(buffer) >= length_len);

    if (read_cb(buffer, 1, length_len, handle) != length_len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    *length = unpack_uint32_(buffer, length_len);

    if (0 != *data)
        free(*data);

    if (0 == (*data = (FLAC__byte*)safe_malloc_add_2op_(*length, /*+*/ 1)))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    if (*length > 0)
    {
        if (read_cb(*data, 1, *length, handle) != *length)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    }

    (*data)[*length] = '\0';

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Picture* block)
{
    FLAC__Metadata_SimpleIteratorStatus status;
    FLAC__byte buffer[4]; /* asserted below that this is big enough */
    FLAC__uint32 len;

    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8);

    FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_TYPE_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->type = (FLAC__StreamMetadata_Picture_Type)unpack_uint32_(buffer, len);

    if ((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, (FLAC__byte**)(&(block->mime_type)), &len, FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
        return status;

    if ((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->description), &len, FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
        return status;

    FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->width = unpack_uint32_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->height = unpack_uint32_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->depth = unpack_uint32_(buffer, len);

    FLAC__ASSERT(FLAC__STREAM_METADATA_PICTURE_COLORS_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8;
    if (read_cb(buffer, 1, len, handle) != len)
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    block->colors = unpack_uint32_(buffer, len);

    /* for convenience we use read_metadata_block_data_picture_cstring_cb_() even though it adds an extra terminating NUL we don't use */
    if ((status = read_metadata_block_data_picture_cstring_cb_(handle, read_cb, &(block->data), &(block->data_length), FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN)) != FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK)
        return status;

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__Metadata_SimpleIteratorStatus read_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__StreamMetadata_Unknown* block, unsigned block_length)
{
    if (block_length == 0)
    {
        block->data = 0;
    }
    else
    {
        if (0 == (block->data = (FLAC__byte*)malloc(block_length)))
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

        if (read_cb(block->data, 1, block_length, handle) != block_length)
            return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
    }

    return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
}

FLAC__bool write_metadata_block_header_(FILE* file, FLAC__Metadata_SimpleIteratorStatus* status, const FLAC__StreamMetadata* block)
{
    FLAC__ASSERT(0 != file);
    FLAC__ASSERT(0 != status);

    if (!write_metadata_block_header_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block))
    {
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
        return false;
    }

    return true;
}

FLAC__bool write_metadata_block_data_(FILE* file, FLAC__Metadata_SimpleIteratorStatus* status, const FLAC__StreamMetadata* block)
{
    FLAC__ASSERT(0 != file);
    FLAC__ASSERT(0 != status);

    if (write_metadata_block_data_cb_((FLAC__IOHandle)file, (FLAC__IOCallback_Write)fwrite, block))
    {
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK;
        return true;
    }
    else
    {
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
        return false;
    }
}

FLAC__bool write_metadata_block_header_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata* block)
{
    FLAC__byte buffer[FLAC__STREAM_METADATA_HEADER_LENGTH];

    FLAC__ASSERT(block->length < (1u << FLAC__STREAM_METADATA_LENGTH_LEN));

    buffer[0] = (block->is_last ? 0x80 : 0) | (FLAC__byte)block->type;
    pack_uint32_(block->length, buffer + 1, 3);

    if (write_cb(buffer, 1, FLAC__STREAM_METADATA_HEADER_LENGTH, handle) != FLAC__STREAM_METADATA_HEADER_LENGTH)
        return false;

    return true;
}

FLAC__bool write_metadata_block_data_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata* block)
{
    FLAC__ASSERT(0 != block);

    switch (block->type)
    {
        case FLAC__METADATA_TYPE_STREAMINFO:
            return write_metadata_block_data_streaminfo_cb_(handle, write_cb, &block->data.stream_info);
        case FLAC__METADATA_TYPE_PADDING:
            return write_metadata_block_data_padding_cb_(handle, write_cb, &block->data.padding, block->length);
        case FLAC__METADATA_TYPE_APPLICATION:
            return write_metadata_block_data_application_cb_(handle, write_cb, &block->data.application, block->length);
        case FLAC__METADATA_TYPE_SEEKTABLE:
            return write_metadata_block_data_seektable_cb_(handle, write_cb, &block->data.seek_table);
        case FLAC__METADATA_TYPE_VORBIS_COMMENT:
            return write_metadata_block_data_vorbis_comment_cb_(handle, write_cb, &block->data.vorbis_comment);
        case FLAC__METADATA_TYPE_CUESHEET:
            return write_metadata_block_data_cuesheet_cb_(handle, write_cb, &block->data.cue_sheet);
        case FLAC__METADATA_TYPE_PICTURE:
            return write_metadata_block_data_picture_cb_(handle, write_cb, &block->data.picture);
        default:
            return write_metadata_block_data_unknown_cb_(handle, write_cb, &block->data.unknown, block->length);
    }
}

FLAC__bool write_metadata_block_data_streaminfo_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_StreamInfo* block)
{
    FLAC__byte buffer[FLAC__STREAM_METADATA_STREAMINFO_LENGTH];
    const unsigned channels1 = block->channels - 1;
    const unsigned bps1 = block->bits_per_sample - 1;

    /* we are using hardcoded numbers for simplicity but we should
     * probably eventually write a bit-level packer and use the
     * _STREAMINFO_ constants.
     */
    pack_uint32_(block->min_blocksize, buffer, 2);
    pack_uint32_(block->max_blocksize, buffer + 2, 2);
    pack_uint32_(block->min_framesize, buffer + 4, 3);
    pack_uint32_(block->max_framesize, buffer + 7, 3);
    buffer[10] = (block->sample_rate >> 12) & 0xff;
    buffer[11] = (block->sample_rate >> 4) & 0xff;
    buffer[12] = ((block->sample_rate & 0x0f) << 4) | (channels1 << 1) | (bps1 >> 4);
    buffer[13] = (FLAC__byte)(((bps1 & 0x0f) << 4) | ((block->total_samples >> 32) & 0x0f));
    pack_uint32_((FLAC__uint32)block->total_samples, buffer + 14, 4);
    memcpy(buffer + 18, block->md5sum, 16);

    if (write_cb(buffer, 1, FLAC__STREAM_METADATA_STREAMINFO_LENGTH, handle) != FLAC__STREAM_METADATA_STREAMINFO_LENGTH)
        return false;

    return true;
}

FLAC__bool write_metadata_block_data_padding_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Padding* block, unsigned block_length)
{
    unsigned i, n = block_length;
    FLAC__byte buffer[1024];

    block;

    memset(buffer, 0, 1024);

    for (i = 0; i < n / 1024; i++)
        if (write_cb(buffer, 1, 1024, handle) != 1024)
            return false;

    n %= 1024;

    if (write_cb(buffer, 1, n, handle) != n)
        return false;

    return true;
}

FLAC__bool write_metadata_block_data_application_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Application* block, unsigned block_length)
{
    const unsigned id_bytes = FLAC__STREAM_METADATA_APPLICATION_ID_LEN / 8;

    if (write_cb(block->id, 1, id_bytes, handle) != id_bytes)
        return false;

    block_length -= id_bytes;

    if (write_cb(block->data, 1, block_length, handle) != block_length)
        return false;

    return true;
}

FLAC__bool write_metadata_block_data_seektable_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_SeekTable* block)
{
    unsigned i;
    FLAC__byte buffer[FLAC__STREAM_METADATA_SEEKPOINT_LENGTH];

    for (i = 0; i < block->num_points; i++)
    {
        /* some MAGIC NUMBERs here */
        pack_uint64_(block->points[i].sample_number, buffer, 8);
        pack_uint64_(block->points[i].stream_offset, buffer + 8, 8);
        pack_uint32_(block->points[i].frame_samples, buffer + 16, 2);
        if (write_cb(buffer, 1, FLAC__STREAM_METADATA_SEEKPOINT_LENGTH, handle) != FLAC__STREAM_METADATA_SEEKPOINT_LENGTH)
            return false;
    }

    return true;
}

FLAC__bool write_metadata_block_data_vorbis_comment_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_VorbisComment* block)
{
    unsigned i;
    const unsigned entry_length_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN / 8;
    const unsigned num_comments_len = FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN / 8;
    FLAC__byte buffer[4]; /* magic number is asserted below */

    FLAC__ASSERT(max(FLAC__STREAM_METADATA_VORBIS_COMMENT_ENTRY_LENGTH_LEN, FLAC__STREAM_METADATA_VORBIS_COMMENT_NUM_COMMENTS_LEN) / 8 == sizeof(buffer));

    pack_uint32_little_endian_(block->vendor_string.length, buffer, entry_length_len);
    if (write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
        return false;
    if (write_cb(block->vendor_string.entry, 1, block->vendor_string.length, handle) != block->vendor_string.length)
        return false;

    pack_uint32_little_endian_(block->num_comments, buffer, num_comments_len);
    if (write_cb(buffer, 1, num_comments_len, handle) != num_comments_len)
        return false;

    for (i = 0; i < block->num_comments; i++)
    {
        pack_uint32_little_endian_(block->comments[i].length, buffer, entry_length_len);
        if (write_cb(buffer, 1, entry_length_len, handle) != entry_length_len)
            return false;
        if (write_cb(block->comments[i].entry, 1, block->comments[i].length, handle) != block->comments[i].length)
            return false;
    }

    return true;
}

FLAC__bool write_metadata_block_data_cuesheet_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_CueSheet* block)
{
    unsigned i, j, len;
    FLAC__byte buffer[1024]; /* asserted below that this is big enough */

    FLAC__ASSERT(sizeof(buffer) >= sizeof(FLAC__uint64));
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8);

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_MEDIA_CATALOG_NUMBER_LEN / 8;
    if (write_cb(block->media_catalog_number, 1, len, handle) != len)
        return false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_LEAD_IN_LEN / 8;
    pack_uint64_(block->lead_in, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) % 8 == 0);
    len = (FLAC__STREAM_METADATA_CUESHEET_IS_CD_LEN + FLAC__STREAM_METADATA_CUESHEET_RESERVED_LEN) / 8;
    memset(buffer, 0, len);
    if (block->is_cd)
        buffer[0] |= 0x80;
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN % 8 == 0);
    len = FLAC__STREAM_METADATA_CUESHEET_NUM_TRACKS_LEN / 8;
    pack_uint32_(block->num_tracks, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    for (i = 0; i < block->num_tracks; i++)
    {
        FLAC__StreamMetadata_CueSheet_Track* track = block->tracks + i;

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_OFFSET_LEN / 8;
        pack_uint64_(track->offset, buffer, len);
        if (write_cb(buffer, 1, len, handle) != len)
            return false;

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUMBER_LEN / 8;
        pack_uint32_(track->number, buffer, len);
        if (write_cb(buffer, 1, len, handle) != len)
            return false;

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_ISRC_LEN / 8;
        if (write_cb(track->isrc, 1, len, handle) != len)
            return false;

        FLAC__ASSERT((FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) % 8 == 0);
        len = (FLAC__STREAM_METADATA_CUESHEET_TRACK_TYPE_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_PRE_EMPHASIS_LEN + FLAC__STREAM_METADATA_CUESHEET_TRACK_RESERVED_LEN) / 8;
        memset(buffer, 0, len);
        buffer[0] = (track->type << 7) | (track->pre_emphasis << 6);
        if (write_cb(buffer, 1, len, handle) != len)
            return false;

        FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN % 8 == 0);
        len = FLAC__STREAM_METADATA_CUESHEET_TRACK_NUM_INDICES_LEN / 8;
        pack_uint32_(track->num_indices, buffer, len);
        if (write_cb(buffer, 1, len, handle) != len)
            return false;

        for (j = 0; j < track->num_indices; j++)
        {
            FLAC__StreamMetadata_CueSheet_Index* index = track->indices + j;

            FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN % 8 == 0);
            len = FLAC__STREAM_METADATA_CUESHEET_INDEX_OFFSET_LEN / 8;
            pack_uint64_(index->offset, buffer, len);
            if (write_cb(buffer, 1, len, handle) != len)
                return false;

            FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN % 8 == 0);
            len = FLAC__STREAM_METADATA_CUESHEET_INDEX_NUMBER_LEN / 8;
            pack_uint32_(index->number, buffer, len);
            if (write_cb(buffer, 1, len, handle) != len)
                return false;

            FLAC__ASSERT(FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN % 8 == 0);
            len = FLAC__STREAM_METADATA_CUESHEET_INDEX_RESERVED_LEN / 8;
            memset(buffer, 0, len);
            if (write_cb(buffer, 1, len, handle) != len)
                return false;
        }
    }

    return true;
}

FLAC__bool write_metadata_block_data_picture_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Picture* block)
{
    unsigned len;
    size_t slen;
    FLAC__byte buffer[4]; /* magic number is asserted below */

    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_TYPE_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_COLORS_LEN % 8);
    FLAC__ASSERT(0 == FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN % 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8);
    FLAC__ASSERT(sizeof(buffer) >= FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN / 8);

    len = FLAC__STREAM_METADATA_PICTURE_TYPE_LEN / 8;
    pack_uint32_(block->type, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_MIME_TYPE_LENGTH_LEN / 8;
    slen = strlen(block->mime_type);
    pack_uint32_(slen, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;
    if (write_cb(block->mime_type, 1, slen, handle) != slen)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_DESCRIPTION_LENGTH_LEN / 8;
    slen = strlen((const char*)block->description);
    pack_uint32_(slen, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;
    if (write_cb(block->description, 1, slen, handle) != slen)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_WIDTH_LEN / 8;
    pack_uint32_(block->width, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_HEIGHT_LEN / 8;
    pack_uint32_(block->height, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_DEPTH_LEN / 8;
    pack_uint32_(block->depth, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_COLORS_LEN / 8;
    pack_uint32_(block->colors, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;

    len = FLAC__STREAM_METADATA_PICTURE_DATA_LENGTH_LEN / 8;
    pack_uint32_(block->data_length, buffer, len);
    if (write_cb(buffer, 1, len, handle) != len)
        return false;
    if (write_cb(block->data, 1, block->data_length, handle) != block->data_length)
        return false;

    return true;
}

FLAC__bool write_metadata_block_data_unknown_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Write write_cb, const FLAC__StreamMetadata_Unknown* block, unsigned block_length)
{
    if (write_cb(block->data, 1, block_length, handle) != block_length)
        return false;

    return true;
}

FLAC__bool write_metadata_block_stationary_(FLAC__Metadata_SimpleIterator* iterator, const FLAC__StreamMetadata* block)
{
    if (0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    if (!write_metadata_block_header_(iterator->file, &iterator->status, block))
        return false;

    if (!write_metadata_block_data_(iterator->file, &iterator->status, block))
        return false;

    if (0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    return read_metadata_block_header_(iterator);
}

FLAC__bool write_metadata_block_stationary_with_padding_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, unsigned padding_length, FLAC__bool padding_is_last)
{
    FLAC__StreamMetadata* padding;

    if (0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    block->is_last = false;

    if (!write_metadata_block_header_(iterator->file, &iterator->status, block))
        return false;

    if (!write_metadata_block_data_(iterator->file, &iterator->status, block))
        return false;

    if (0 == (padding = FLAC__metadata_object_new(FLAC__METADATA_TYPE_PADDING)))
        return FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;

    padding->is_last = padding_is_last;
    padding->length = padding_length;

    if (!write_metadata_block_header_(iterator->file, &iterator->status, padding))
    {
        FLAC__metadata_object_delete(padding);
        return false;
    }

    if (!write_metadata_block_data_(iterator->file, &iterator->status, padding))
    {
        FLAC__metadata_object_delete(padding);
        return false;
    }

    FLAC__metadata_object_delete(padding);

    if (0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    return read_metadata_block_header_(iterator);
}

FLAC__bool rewrite_whole_file_(FLAC__Metadata_SimpleIterator* iterator, FLAC__StreamMetadata* block, FLAC__bool append)
{
    FILE* tempfile;
    char* tempfilename;
    int fixup_is_last_code = 0; /* 0 => no need to change any is_last flags */
    off_t fixup_is_last_flag_offset = -1;

    FLAC__ASSERT(0 != block || append == false);

    if (iterator->is_last)
    {
        if (append)
        {
            fixup_is_last_code = 1; /* 1 => clear the is_last flag at the following offset */
            fixup_is_last_flag_offset = iterator->offset[iterator->depth];
        }
        else if (0 == block)
        {
            simple_iterator_push_(iterator);
            if (!FLAC__metadata_simple_iterator_prev(iterator))
            {
                simple_iterator_pop_(iterator);
                return false;
            }
            fixup_is_last_code = -1; /* -1 => set the is_last the flag at the following offset */
            fixup_is_last_flag_offset = iterator->offset[iterator->depth];
            if (!simple_iterator_pop_(iterator))
                return false;
        }
    }

    if (!simple_iterator_copy_file_prefix_(iterator, &tempfile, &tempfilename, append))
        return false;

    if (0 != block)
    {
        if (!write_metadata_block_header_(tempfile, &iterator->status, block))
        {
            cleanup_tempfile_(&tempfile, &tempfilename);
            return false;
        }

        if (!write_metadata_block_data_(tempfile, &iterator->status, block))
        {
            cleanup_tempfile_(&tempfile, &tempfilename);
            return false;
        }
    }

    if (!simple_iterator_copy_file_postfix_(iterator, &tempfile, &tempfilename, fixup_is_last_code, fixup_is_last_flag_offset, block == 0))
        return false;

    if (append)
        return FLAC__metadata_simple_iterator_next(iterator);

    return true;
}

void simple_iterator_push_(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(iterator->depth + 1 < SIMPLE_ITERATOR_MAX_PUSH_DEPTH);
    iterator->offset[iterator->depth + 1] = iterator->offset[iterator->depth];
    iterator->depth++;
}

FLAC__bool simple_iterator_pop_(FLAC__Metadata_SimpleIterator* iterator)
{
    FLAC__ASSERT(iterator->depth > 0);
    iterator->depth--;
    if (0 != fseeko(iterator->file, iterator->offset[iterator->depth], SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }

    return read_metadata_block_header_(iterator);
}

/* return meanings:
 * 0: ok
 * 1: read error
 * 2: seek error
 * 3: not a FLAC file
 */
unsigned seek_to_first_metadata_block_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Seek seek_cb)
{
    FLAC__byte buffer[4];
    size_t n;
    unsigned i;

    FLAC__ASSERT(FLAC__STREAM_SYNC_LENGTH == sizeof(buffer));

    /* skip any id3v2 tag */
    errno = 0;
    n = read_cb(buffer, 1, 4, handle);
    if (errno)
        return 1;
    else if (n != 4)
        return 3;
    else if (0 == memcmp(buffer, "ID3", 3))
    {
        unsigned tag_length = 0;

        /* skip to the tag length */
        if (seek_cb(handle, 2, SEEK_CUR) < 0)
            return 2;

        /* read the length */
        for (i = 0; i < 4; i++)
        {
            if (read_cb(buffer, 1, 1, handle) < 1 || buffer[0] & 0x80)
                return 1;
            tag_length <<= 7;
            tag_length |= (buffer[0] & 0x7f);
        }

        /* skip the rest of the tag */
        if (seek_cb(handle, tag_length, SEEK_CUR) < 0)
            return 2;

        /* read the stream sync code */
        errno = 0;
        n = read_cb(buffer, 1, 4, handle);
        if (errno)
            return 1;
        else if (n != 4)
            return 3;
    }

    /* check for the fLaC signature */
    if (0 == memcmp(FLAC__STREAM_SYNC_STRING, buffer, FLAC__STREAM_SYNC_LENGTH))
        return 0;
    else
        return 3;
}

unsigned seek_to_first_metadata_block_(FILE* f)
{
    return seek_to_first_metadata_block_cb_((FLAC__IOHandle)f, (FLAC__IOCallback_Read)fread, fseek_wrapper_);
}

FLAC__bool simple_iterator_copy_file_prefix_(FLAC__Metadata_SimpleIterator* iterator, FILE** tempfile, char** tempfilename, FLAC__bool append)
{
    const off_t offset_end = append ? iterator->offset[iterator->depth] + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (off_t)iterator->length : iterator->offset[iterator->depth];

    if (0 != fseeko(iterator->file, 0, SEEK_SET))
    {
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }
    if (!open_tempfile_(iterator->filename, iterator->tempfile_path_prefix, tempfile, tempfilename, &iterator->status))
    {
        cleanup_tempfile_(tempfile, tempfilename);
        return false;
    }
    if (!copy_n_bytes_from_file_(iterator->file, *tempfile, offset_end, &iterator->status))
    {
        cleanup_tempfile_(tempfile, tempfilename);
        return false;
    }

    return true;
}

FLAC__bool simple_iterator_copy_file_postfix_(FLAC__Metadata_SimpleIterator* iterator, FILE** tempfile, char** tempfilename, int fixup_is_last_code, off_t fixup_is_last_flag_offset, FLAC__bool backup)
{
    off_t save_offset = iterator->offset[iterator->depth];
    FLAC__ASSERT(0 != *tempfile);

    if (0 != fseeko(iterator->file, save_offset + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (off_t)iterator->length, SEEK_SET))
    {
        cleanup_tempfile_(tempfile, tempfilename);
        iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
        return false;
    }
    if (!copy_remaining_bytes_from_file_(iterator->file, *tempfile, &iterator->status))
    {
        cleanup_tempfile_(tempfile, tempfilename);
        return false;
    }

    if (fixup_is_last_code != 0)
    {
        /*
         * if code == 1, it means a block was appended to the end so
         *   we have to clear the is_last flag of the previous block
         * if code == -1, it means the last block was deleted so
         *   we have to set the is_last flag of the previous block
         */
        /* MAGIC NUMBERs here; we know the is_last flag is the high bit of the byte at this location */
        FLAC__byte x;
        if (0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET))
        {
            cleanup_tempfile_(tempfile, tempfilename);
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
            return false;
        }
        if (fread(&x, 1, 1, *tempfile) != 1)
        {
            cleanup_tempfile_(tempfile, tempfilename);
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        }
        if (fixup_is_last_code > 0)
        {
            FLAC__ASSERT(x & 0x80);
            x &= 0x7f;
        }
        else
        {
            FLAC__ASSERT(!(x & 0x80));
            x |= 0x80;
        }
        if (0 != fseeko(*tempfile, fixup_is_last_flag_offset, SEEK_SET))
        {
            cleanup_tempfile_(tempfile, tempfilename);
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR;
            return false;
        }
        if (local__fwrite(&x, 1, 1, *tempfile) != 1)
        {
            cleanup_tempfile_(tempfile, tempfilename);
            iterator->status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
            return false;
        }
    }

    fclose(iterator->file);

    if (!transport_tempfile_(iterator->filename, tempfile, tempfilename, &iterator->status))
        return false;

    if (iterator->has_stats)
        set_file_stats_(iterator->filename, &iterator->stats);

    if (!simple_iterator_prime_input_(iterator, !iterator->is_writable))
        return false;
    if (backup)
    {
        while (iterator->offset[iterator->depth] + (off_t)FLAC__STREAM_METADATA_HEADER_LENGTH + (off_t)iterator->length < save_offset)
            if (!FLAC__metadata_simple_iterator_next(iterator))
                return false;
        return true;
    }
    else
    {
        /* move the iterator to it's original block faster by faking a push, then doing a pop_ */
        FLAC__ASSERT(iterator->depth == 0);
        iterator->offset[0] = save_offset;
        iterator->depth++;
        return simple_iterator_pop_(iterator);
    }
}

FLAC__bool copy_n_bytes_from_file_(FILE* file, FILE* tempfile, off_t bytes, FLAC__Metadata_SimpleIteratorStatus* status)
{
    FLAC__byte buffer[8192];
    size_t n;

    FLAC__ASSERT(bytes >= 0);
    while (bytes > 0)
    {
        n = min(sizeof(buffer), (size_t)bytes);
        if (fread(buffer, 1, n, file) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        }
        if (local__fwrite(buffer, 1, n, tempfile) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
            return false;
        }
        bytes -= n;
    }

    return true;
}

FLAC__bool copy_n_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, off_t bytes, FLAC__Metadata_SimpleIteratorStatus* status)
{
    FLAC__byte buffer[8192];
    size_t n;

    FLAC__ASSERT(bytes >= 0);
    while (bytes > 0)
    {
        n = min(sizeof(buffer), (size_t)bytes);
        if (read_cb(buffer, 1, n, handle) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        }
        if (temp_write_cb(buffer, 1, n, temp_handle) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
            return false;
        }
        bytes -= n;
    }

    return true;
}

FLAC__bool copy_remaining_bytes_from_file_(FILE* file, FILE* tempfile, FLAC__Metadata_SimpleIteratorStatus* status)
{
    FLAC__byte buffer[8192];
    size_t n;

    while (!feof(file))
    {
        n = fread(buffer, 1, sizeof(buffer), file);
        if (n == 0 && !feof(file))
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        }
        if (n > 0 && local__fwrite(buffer, 1, n, tempfile) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
            return false;
        }
    }

    return true;
}

FLAC__bool copy_remaining_bytes_from_file_cb_(FLAC__IOHandle handle, FLAC__IOCallback_Read read_cb, FLAC__IOCallback_Eof eof_cb, FLAC__IOHandle temp_handle, FLAC__IOCallback_Write temp_write_cb, FLAC__Metadata_SimpleIteratorStatus* status)
{
    FLAC__byte buffer[8192];
    size_t n;

    while (!eof_cb(handle))
    {
        n = read_cb(buffer, 1, sizeof(buffer), handle);
        if (n == 0 && !eof_cb(handle))
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR;
            return false;
        }
        if (n > 0 && temp_write_cb(buffer, 1, n, temp_handle) != n)
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR;
            return false;
        }
    }

    return true;
}

FLAC__bool open_tempfile_(const char* filename, const char* tempfile_path_prefix, FILE** tempfile, char** tempfilename, FLAC__Metadata_SimpleIteratorStatus* status)
{
    static const char* tempfile_suffix = ".metadata_edit";
    if (0 == tempfile_path_prefix)
    {
        if (0 == (*tempfilename = (char*)safe_malloc_add_3op_(strlen(filename), /*+*/ strlen(tempfile_suffix), /*+*/ 1)))
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
            return false;
        }
        strcpy(*tempfilename, filename);
        strcat(*tempfilename, tempfile_suffix);
    }
    else
    {
        const char* p = strrchr(filename, '/');
        if (0 == p)
            p = filename;
        else
            p++;

        if (0 == (*tempfilename = (char*)safe_malloc_add_4op_(strlen(tempfile_path_prefix), /*+*/ strlen(p), /*+*/ strlen(tempfile_suffix), /*+*/ 2)))
        {
            *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR;
            return false;
        }
        strcpy(*tempfilename, tempfile_path_prefix);
        strcat(*tempfilename, "/");
        strcat(*tempfilename, p);
        strcat(*tempfilename, tempfile_suffix);
    }

    if (0 == (*tempfile = fopen(*tempfilename, "w+b")))
    {
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE;
        return false;
    }

    return true;
}

FLAC__bool transport_tempfile_(const char* filename, FILE** tempfile, char** tempfilename, FLAC__Metadata_SimpleIteratorStatus* status)
{
    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != tempfile);
    FLAC__ASSERT(0 != *tempfile);
    FLAC__ASSERT(0 != tempfilename);
    FLAC__ASSERT(0 != *tempfilename);
    FLAC__ASSERT(0 != status);

    fclose(*tempfile);
    *tempfile = 0;

    #if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__ || defined __EMX__
    /* on some flavors of windows, rename() will fail if the destination already exists */
    if (_unlink(filename) < 0)
    {
        cleanup_tempfile_(tempfile, tempfilename);
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR;
        return false;
    }
    #endif

    /*@@@ to fully support the tempfile_path_prefix we need to update this piece to actually copy across filesystems instead of just rename(): */
    if (0 != rename(*tempfilename, filename))
    {
        cleanup_tempfile_(tempfile, tempfilename);
        *status = FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR;
        return false;
    }

    cleanup_tempfile_(tempfile, tempfilename);

    return true;
}

void cleanup_tempfile_(FILE** tempfile, char** tempfilename)
{
    if (0 != *tempfile)
    {
        fclose(*tempfile);
        *tempfile = 0;
    }

    if (0 != *tempfilename)
    {
        _unlink(*tempfilename);
        free(*tempfilename);
        *tempfilename = 0;
    }
}

FLAC__bool get_file_stats_(const char* filename, struct stat* stats)
{
    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != stats);
    return (0 == stat(filename, stats));
}

void set_file_stats_(const char* filename, struct stat* stats)
{
    struct utimbuf srctime;

    FLAC__ASSERT(0 != filename);
    FLAC__ASSERT(0 != stats);

    srctime.actime = stats->st_atime;
    srctime.modtime = stats->st_mtime;
    _chmod(filename, stats->st_mode);
    utime(filename, &srctime);
    #if !defined _MSC_VER && !defined __BORLANDC__ && !defined __MINGW32__ && !defined __EMX__
        () chown(filename, stats->st_uid, -1);
    ()chown(filename, -1, stats->st_gid);
    #endif
}

int fseek_wrapper_(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
{
    return fseeko((FILE*)handle, (off_t)offset, whence);
}

FLAC__int64 ftell_wrapper_(FLAC__IOHandle handle)
{
    return ftello((FILE*)handle);
}

FLAC__Metadata_ChainStatus get_equivalent_status_(FLAC__Metadata_SimpleIteratorStatus status)
{
    switch (status)
    {
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_OK:
            return FLAC__METADATA_CHAIN_STATUS_OK;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ILLEGAL_INPUT:
            return FLAC__METADATA_CHAIN_STATUS_ILLEGAL_INPUT;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_ERROR_OPENING_FILE:
            return FLAC__METADATA_CHAIN_STATUS_ERROR_OPENING_FILE;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_A_FLAC_FILE:
            return FLAC__METADATA_CHAIN_STATUS_NOT_A_FLAC_FILE;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_NOT_WRITABLE:
            return FLAC__METADATA_CHAIN_STATUS_NOT_WRITABLE;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_BAD_METADATA:
            return FLAC__METADATA_CHAIN_STATUS_BAD_METADATA;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_READ_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_READ_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_SEEK_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_SEEK_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_WRITE_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_WRITE_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_RENAME_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_RENAME_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_UNLINK_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_UNLINK_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_MEMORY_ALLOCATION_ERROR:
            return FLAC__METADATA_CHAIN_STATUS_MEMORY_ALLOCATION_ERROR;
        case FLAC__METADATA_SIMPLE_ITERATOR_STATUS_INTERNAL_ERROR:
        default:
            return FLAC__METADATA_CHAIN_STATUS_INTERNAL_ERROR;
    }
}